Apparatus for continuously enameling thin sheet metal



March 17, 1953 R. e. CALTON 2,631,561

APPARATUS FOR CONTINUOUSLY ENAMELING THIN SHEET METAL 2 SHEETS-SHEET lFiled Jan. .3, 1951 llvvewroe Poet/er 6" mire/v T70R17! Y1 mum March 17,1953 R. G. CALTON APPARATUS FOR CONTINUOUSLY ENAMELING THIN SHEET METALFiled Jan. 5, 1951 2 SHEETSSl-IEET 2 Patented Mar. 17, 1953 APPARATUSFOR CONTINUOUSLY ENAMEL- ING THIN SHEET METAL Robert G. Calton,Nashville, Tenn.

Application January 3, 1951, Serial N 0. 204,156

2 Claims. 1

This invention relates to apparatus for porcelain enameling sheet metaland has more particular reference to apparatus for continuously applyingporcelain enamel to thin sheet steel or thin sheet iron.

In the firing of porcelain enameled sheet iron of 20 gauge or lighter,it has been the practice to either support the article in a horizontalplane on spaced pins or the like, or to hang the article from hooks on achain which carries the articles through a firing zone. It has neverbeen possible heretofore to fire large flat pieces thinner than 20 gaugeby either of these procedures without warpage. If the workpiece hasrested on the conventional firing pins in a horizontal position, thebase metal was softened during th firing operation to an extentsufiicient to cause sagging in the areas between the pins and noticeabledeformation in the supported areas. A sheet thus fired with the basemetal deformed will always show the presence of such deformed areabecause of the reflective nature of the porcelain enamel coating.Furthermore, the cooled sheet was severely warped and did not present anadequate flat surface. from hooks and fired by being carried through afurnace, the sheets usually warped, due, not only to the weight of thesheet itself, but also the inherent stresses which are present in thesheet. Thin sheets, that is, thinner than 20 gauge, when fired. in thisWay, also tend to exhibit an overall "crinkled effect due to th unequalsoftening of the sheet in local areas and the internal stresses in thesheet, as aforesaid.

It is, therefore, a principal object of this invention to provide noveland improved apparatus for continuously porcelain enameling sheet metalranging from 20 to 40 gauge, without the enameled sheet metal showingareas of deformation.

Another object of the invention is to provide apparatus, as abovecharacterized, including means for controlling the tension of the movingsheet as it moves through the firing furnace to prevent buckling andwarping thereof, due to the firing temperature.

A further object of the invention is to provide apparatus, as abovecharacterized, including a firing furnace having an arch. for supportingand guiding the sheet during its travel therethrough.

Other objects and advantages of the invention will appear in thespecification when considered in connection with the accompanyingdrawings, wherein:

Fig. l is a diagrammatic elevational view of the apparatus of theinvention, with parts broken When the sheets have been hung away to showthe interior of certain of the elements;

Fig. 2 is a diagrammatic plan view of the apparatus shown in Fig. l;

Fig. 3 is a detailed perspective view showing the manner in which therollers are mounted; and

Fig. 4 is a detailed perspective view showing the manner in which thetension control idle rollers are mounted.

This invention is related to the subject matter of my co-pendingapplication, Ser. No. 125,987, filed Nov. 2, 1949, and entitled Methodsof and Apparatus for Porcelain Enameling Sheet Metal.

The present invention, insofar as it concerns the application ofvitreous enamel or frit paste to a continuously moving thin sheet ofmetal and the firing of the coated sheet, is similar to the inventiondisclosed and claimed in my said copendins' application. Here, however,the similarity ceases, and many improvements and advantageous featuresare incorporated in the invention of the present application.

Referring now to the drawings, and more particularly to Figs. 1 2, thereis shown a coiled roll. Ill of sheet metal ll, ranging from 20 to 40gauge, mounted on a horizontal spindle Ill. The sheet passes throughdriven rollers I3 and then through a vat Is filled with a nickel sulfatesolution of approximately 12 oz./ga1lon, the sheet being held below thesurface of the solution by means of idle roller I 5.

From the nickel sulfate solution, the sheet passes over idle roller It,then through a drying chamber H, which may comprise heat lamps l8, orother suitable heatin elements, Where the sheet is dried. The excessnickel sulfate solution is wiped off both sides of the sheet as itemerges from the vat. From the drying chamber, the sheet passes throughdriven. rollers I9 into and through a vat 2i! filled with ground coatenamel slip or frit paste of any suitable composition, where the sheetis coated with a coating of the slip. The sheet is held below thesurface of the slip by means of idle roller 2 i.

From the coating vat 20, the sheet passes over a rubber stripper orsqueegee 22, which removes the enamel slip from the bottom of the sheet,and then through a firing furnace 23, shown diagrammatically as beingheated electrically by resistors 2d. It is to be understood that theheat may be applied in any other suitable manner.

During its passage through the firing furnace, the sheet is supported byand slides over the up per surface of a metal arch 25. The arch 25 iswider than the sheet and is preferably made in three sections, anintermediate section 26 made of nickel alloy to Withstand the firingtemperature, and end sections 21 made of any suitable materialpreferably metal. The upper surface of the arch is flat in transversecross section.

rom the furnace 23 the fired sheet passes under 2. sag control device28, through driven rollers 29, into a second coating vat identical tothe vat 2d. The second coating vat is filled with cover coat enamel slipor frit paste of the desired color and composition. The sheet is heldbelow the surface of the slip by means of idle roller 3i From thecoating vat 3d, the sheet passes over a rubber stripper or squeegee 32,which removes the enamel slip from the bottom of the sheet, and thenthrough a second firing furnace 33, which is identical in constructionto the first firing furnace 23. During its passage through the secondfiring furnace 33, the sheet is supported by and slides over the uppersurface of a metal arch which is identical in construction to the arch25 in the first firing furnace.

The sheet emerges from the second firing furnace 33 as the finishedproduct. As the finished product emerges from the second firing furnace33, it passes under a second sag control device 35 and then throughdriven rollers 36. The sheet emerging from the driven rollers 36 may becut to suitable length or rolled into a coil 31.

The driven rollers i3, l 9, 29 and 36 are identical in construction and,as shown in Fig. 3, each comprises a lower roller 38 journaled in fixedbearing blocks 59 supported by a suitable frame 49; an adjustable upperroller 4| journaled in bearing blocks l2 vertically slidably mounted inthe frame id and carrying compression springs 43; vertically adjustablesliding blocks 44 slidably mounted in the frame M and engaging the upperends of the coiled springs; and adjusting screws 45 for verticallyadjusting the position of the sliding blocks so that the springs 43 willtightly and resiliently hold the upper roller in engagement with thelower roller. Both the upper and lower rollers are preferably made ofresilient composition material and may be covered with asbestos or thelike.

The driven rollers l3 and l9 are driven through suitable gearing such asa shaft having gears 31 and 5S fixed thereto and adapted to engage anddrive suitable gears and 5!) on the roller shafts of the fixed roller ofeach pair of driven rollers 53 and 59, respectively. The shaft 46 isrotated by a constant speed motor 5! through suitable reduction gearing52.

The driven rollers 29 and 36 are driven at constant speed by motors 53and 54 through suitable reduction gearing 55, 56 connected to the lowerrollers of the respective pairs of driven rollers.

The sag control devices 23 and 35 are identical in construction and, asshown in Fig. 4, each comprises an idle roller 5? journaled between theouter ends of arms 58, 59 pivotally mounted on suitable frames Therollers 57 ride freely on the upper surface of the moving sheet and areof SllfTiCli-llflt weight to hold the sheet taut against the uppersurfaces of the arches in the respective furnaces. Added weight may beapplied to the roller shafts to provide for the desired tensioning ofthe sheet.

Positioned above the arm 53 of the roller 5'! of the slack controldevice 28 is a limit switch 6| connected upon being operated to startmotor 5| which operates the driven rollers l3 and I9.

Positioned below the arm 58 of the roller 51 of the slack control device28 is a second limit switch 62, connected upon being operated to stopthe motor 5|. The construction and arrangement is such that with allmotors running and the sheet moving through the apparatus, any slackdeveloped in the sheet, due to its expansion in the first firingfurnace, Will cause the arm 58 carrying the roller 51 to move downwardlyand engage the limit switch 62 to stop the motor 5|, thus permitting thedriven rollers 29 and 35 to take up the slack. When the arm 58 movesupwardly as the slack is taken up, it will engage the limit switch SIand start the motor 5! so that the sheet will move through the firstfurnace along its predetermined line of travel.

The slack control device 35 operates in a similar manner to take up anyslack developed due to expansion of the sheet in the second furnace.Positioned above the arm 58 carrying the idle roller 5? of the slackcontrol device 35 is a limit switch 53 connected when operated to startmotors 5i and 53, which drive the driven rollers l3, l9 and 29.Positioned below the arm 58 of the slack control device 35 is a secondlimit switch connected when operated to stop motors 5! and 53.

When the sheet expands, due to the tempera ture in the second firingfurnace, the arm 58 engages the limit switch 64 and stops the motors 5iand 53. The motor 5 1 continues to run and take up the slack in thesheet. When the arm 58 moves upward into engagement with the limitswitch 63, the motors 5! and 53 will be started again and the sheet willmove through the second furnace along its predetermined line of travel.i

From the foregoing description, it will be readily seen that there hasbeen provided novel and improved apparatus for continuously porcelainenameling thin sheet iron, including means for maintaining the sheetunder sufiicient tension while being fired to prevent buckling andwarping, whereby the finished product will be free of warping or areasof deformation and have a continuous glossy surface free of blemishes.

While the ground coat and cover coat of frit paste or slip has beenshown as being applied by dipping, obviously, these coats may be sprayedon just before the moving sheet enters the firing chamber, if desired.

Obviously, the invention is not restricted to the particular embodimentthereof herein shown and described.

What is claimed is:

1. For use in apparatus for continuously porcelain enameling sheet ironof the class wherein a coil of 20-40 gauge sheet iron mounted on ahorizontal spindle is fed by means of a plurality of horizontally spacedpairs of gripping and feeding rollers in succession through means forapplying frit paste to the upper surface of the moving iron sheet andthrough a furnace having substantially horizontally aligned inlet andoutlet openings therein, in which the frit paste is fused on the movingiron sheet; the combination with said furnace of means for preventingthe moving iron sheet from buckling and warping during its passagethrough the furnace, including an arched support mounted in said furnaceand extending between the inlet and outlet openings therein and overwhich the moving iron sheet is adapted to slide; and a tensioning memberengaging the upper surface of said moving iron sheet for holding thesheet taut in sliding engagement with the upper surface of the archedsupport as it passes through the furnace, whereby the sheet will beprevented from buckling and warping due to the high heat in the furnace.

2. Apparatus as set forth in claim 1, wherein said tensioning membercomprises a pivotally mounted idle tensioning roller.

ROBERT G. CALTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 6 UNITED STATES PATENTS Name Date Nuernberg July 1'7, 1934Callinan Feb. 5, 1946 Calton Sept. 30, 1947 Francis Apr. 20, 1948 MartinMay 3, 1949 Calton Aug. 30, 1949

